Cathode ray tube



Feb. 18, 1941. e. A. DEICHMAN CATHODE RAY TUBE Filed Feb. 11, 1938 3Sheets-Sheet 1 ATTORNEY 1941- G. A. DEICHMAN CATHODE RAY TUBE Filed Feb.11, 1938 3 Sheets-Sheet 2 INVENTOR Feb. 18, 1941. DEICHMAN 2,232,098

ckrnonm RAY TUBE Filed Feb. 11, 1938 3 Sheets-Sheat 3 INVENTOR ATTORNEYPatented Feb. 18 1941 UNITED STATES 2,232,098 I CATHODE BAY TUBE GeorgeA. Deichman, Eidgway. Pa, assignor to Hygrade Sylvania Corporation,Salem, Mass., a corporation of Massachusetts Application February 11,1938, Serial No. 190,016

nciaims.

Another object is to provide an improved manner of strengthening thefunnel-shaped metal wall section of a cathode ray tube and the like.

A further object is to provide a method of fabricating the metalenvelope of a large metal cathode ray tube whereby it is free fromundesirable strains or localized weaknesses ordinarily caused by theforming and shaping operations. As a result the finished tube can behighly evacuated and is capable of withstanding the outside atmosphericpressure during and after exhaust,

while utilizing a minimum thickness of metal stock.

" A feature of the'invention relates to a cathode ray tube envelopehaving a metal funnel-shaped portion substantially rectangular in crosssection and provided with reenforcing ribs of novel I formation.

Another feature relates to an improved method of forming a metal-framedwindow for a cathode ray tube whereby the existence of local stresses inthe glass of the window are substantiall eliminated.

Another feature relates to an improved form of resilient gasket forevacuated tubes and the like.

Another feature relates to an improved formaing a flared glass neck tothe constricted end of the metal funnel-shaped portion of a cathode raytube or the like.

Another feature relates to a method of forming the seamless metalfunnel-shaped portion of a cathode ray tube by a drawing process wherebythe enlarged end can be formed with a uniformly flat supporting rim fora relatively massive metal-framed glass window.

A further feature is to provide an improved construction of cathode raytube of the type having a relatively massive glass window separate fromthe metal body portion of the envelope, wherein the dimensions andsurface contours 5.5 are formed with a high degree of accuracy and tionof metal sealing ring for hermetically joinas a result of which the tubeis capable of withstanding outside atmospheric pressures without dangerof subjecting the sealed joints to unequal strains.

. A still further feature relates to the novel 'or- .I ganization,arrangement and relative location of parts which constitute an improvedcathode ray tube of the composite metal-glass envelope type. Theinvention pertains to a tube of the type disclosed in Patent No.2,178,826, and while the 1. present disclosure refers to a cathode raytube, it is understood that by this is meant any tube of the compositemetal-glass type wherein a glass window or closure member is formed as aseparate element from the main body of the tube; 1| and includes suchdevices as television tubes for reception or transmission, for exampleIconoscopes, dissector tubes, as well as oscillographs or the like. Incertain of its aspects the invention is not limited to cathode ray tubesand is j capable of application to other devices having a compositeglass-metal evacuated envelope. Ac cordingly, other features andadvantages not specifically enumerated will be apparent afterconsideration of the following detailed descripll tions and the appendedclaims. In the draw-' ings:

Figs. 1, 2 and 3 are diagrams explanatory of three successive steps inthe formation of the funnel-shaped part of the cathode ray tube en- 8.velope according to the invention.

Fig. 4 shows part of the envelope after the final drawing operation.

Fig. 5 is a cross sectional view of Fig. 4- taken along the line 5-5thereof.

Fig. 6 is a cross sectional view of Fig. 4 taken along the line 6-6thereof.

Fig. '7 is a sectional view of the member of 'Fig. 4 after the ribstriking and shoulder formspecially shaped sealing ring according to then v invention.

Fig. 12 is a sectional view of the other part of the special sealingring.

Fig. 13 is a view of the finished funnel-shaped portion of the envelopeand forming with Figs.

11 and 12 an exploded view of the method of assembly.

Fig. 14 is an assembled view of the parts shown in Figs. 11, 12 and 13.

Fig. 15 is a cross sectional view of a special jig for centering andsupporting the parts during certain of the welding operations.

Fig. 16 is a perspective view partly in section of the finished metalframed window according to the invention.

Fig. 17 is a diagrammatic view to explain the manner of forming theflattened rim on the glass window.

Fig. 18 is a view of part of the resilient gasket according to theinvention.

Fig. 19 is a view partly in section of a complete cathode ray tubeenvelope incorporating the various features of the invention.

In general the tube (Fig. 19) according to the invention, comprises anelongated glass neck I terminating in a flare 2, wherein or adjacent towhich are located the usual beam deflecting means. It will be understoodthat the deflecting means may be either pairs of coordinateelectrostatic deflecting plates mounted within the glass flare 2, or acombination of deflecting plates within the flare 2 and a pair ofelectromagnetic poles 3, 4 for producing a deflecting field coordinateto that produced by the electrostatic plates. The main body portion ofthe tube envelope consists preferably of a single-piece seamlessfunnelshaped section 5 of sheet steel or other suitable strong metal.Preferably, although not necessarily, section 5 is formed, for thegreater part of its length, of rectangular cross section with thecorners rounded as shown in Fig. 5, while the 1 reduced end portion ofsection 5 gradually tapers down to a circular cross section as shown inFig. 6. In order that the section 5 may be sealed to the glass flare 2in a vacuum-tight manner, there is interposed a special bi-part sealingring I, the part 8 of which has substantially the same coefficient ofexpansion as the glass 2. For example if the flare 2 is of a glass suchas Corning 705 AJ glass, part 8 may be of Kovar analloy consisting ofapproximately 18% cobalt, 28% nickel and 54% iron, and the part 9 may beof steel or other suitable metal. Preferably, although not necessarily,the flare 2 is preformed to the desired accuracy and is sealed coaxiallyto the part 8 in the manner described in detail in Patent No. 2,194,418.Part 9 at its enlarged end is welded preierably by seam welding, to thereduced end of section 5. The enlarged end of section 5 is closed ofi ina vacuum-tight manner by a relatively massive glass window I 0 throughthe intermediary of a metal flange Ii carried by the window, and acooperating flange I! on section 5, the flanges i0 and I: being seamwelded to provide a vacuum-tight seal. Preferably a special resilientgasket I3 is provided between the flattened rim H on the window and theshoulder I. It will be understood of course that any wellknown form ofelectron gun or ray-developing means and associated intensity controland focussing electrodes are mounted within the neck I, and that asuitable pronged contact base I5 is fastened to the end of the tube withthe prongs connected to the various electrodes. A typical form ofelectron gun and electrode assembly that may be used is disclosed inPatent No. 2,211,613.

It will also be understood that a coating of suitable material whichfluoresccs under impact of the rays, is applied to the inner face ofwindow iii in any manner well known in the art.

While the invention is not necessarily limited to tubes of any specialdimensions it finds its primary utility in tubes of relatively largewindow area. For example, window I0 may be of the order of 10 inches by12 inches diagonally, and since the tube is highly evacuated, it isapparent that great precautions must be taken to ensure not only againstthe collapse of the tube walls under atmospheric pressure, but also toensure that even though the tube does not collapse, the strains areuniformly distributed throughout the various Joints and seals betweenthe metal-to-metal parts, as well as between the metal-to-glass parts. Ihave found that seemingly minor changes in the shaping and formation ofthe various parts may mean the difference between tubes which arecapable of fabrication and assembly in large quantities with uniformreliability, as against tubes which are unreliable as regards mechanicalstrength and maintenance of the vacuum.

I have also found that it is highly important to provide a proper matingfit between the sections 5 and 9 if a true coaxial seal is to be made.It is extremely difiicult to produce relatively large tubular sheetmetal boxes such as section I with the desired degree of uniformity asregards inside and outside diameter, to meet the stringent requirementsof cathode ray tube technique. If the sections 5 and 9 are made withsubstantially straight or parallel overlapping fits, it requiresexceedingly difficult control of dimensions in order to ensure avacuum-tight weld, particularly where seam-welding is employed. I havefound that by giving the overlapping or mating parts of the sections 5and 9, a complementary taper which is different from the main taper ofsection 5, it is possible to compensate for slight differences in insideand outside diameters; to avoid likelihood of the sections not fittingtogether properly; and to achieve more uniform seam-welding.

Preferably the taper at the overlapping portions of members 5 and 9 tobe welded, is slightly less than the taper of the main section 8, sothat the inner welding mandrel need contact only with the area to bewelded, thus prolonging the life of the mandrel and decreasing itsinitial cost since it need not be made in segments. Furthermore, thewelding operation is simplified since it is not necessary to employcomplicated clamping tools to hold the sections in the proper relativepositions to each other during the seam welding. I have also found thatin order to produce a tube which can be duplicated in large scaleproduction with uniform electrical and mechanical characteristics it isnecessary to have the various metal parts as well as the glass flare 2perfectly coaxial during the seam welding operation. This isaccomplished by utilizing a preliminary "basting welding while the partsare held perfectly coaxial in a specially designed jig.

Preferably the main section 5 is formed as a single piece seamless metalmember by a special deep drawing process. For this purpose a sheet steelblank is subjected in successive steps to a plurality of deep drawingoperations. I have found that in order to produce a finished sectionwhich is substantially entirely free from undesirable recrystallizationand oxidizing, it is necessary to effect the drawing operation inseparate stages and to subject the section to an annealing and picklingoperation before each drawing stage. It is also important that thesection 5 be formed with a perfectly flat flange i2 and a perfectly flatshoulder ii. For this purpose the original sheet steel blankis rigidlyclamped around its periphery between flat clamping members l3, l1(Fig. 1) during each deep drawing stage. Preferably, although notlimited thereto, the section 8 is formed in six successive deep drawingsteps, the results of the first, second, third and final steps beingshown in Figs. 1, 2, 8 and 4 respectively. The deep drawing dies for thesuccessive steps are so designed that the greater part of the length ofthe finished section is substantially rectangular in cross section withrounded corners as shown in Fig. 5. and at the reduced end it mergesinto a circular cross section as shown in Fig. 6. In order to avoidrecrystallization and incipient oxidation at the surface of the section5 during its formation, the blank is annealed and pickled in anywell-known manner before each deep drawing operation.

The deep drawn member of Fig. 4 is then subjected to a shoulder formingand rib striking operation whereby the section is formed on its flatsides with a series of parallel ribs 18 (Figs. 7 and 19) and the flangei2 is formed with a flat shoulder I9. Preferably the ribs II are of thecross sectional shape shown in Fig. 9 from which it will be seen thatthe face 28 of each rib is almost parallel to the longitudinal axis ofthe section 5 while the face 2i is substantially at right angles to thelongitudinal axis of the section. Because of the extremely small anglethe faces 28 make with the longitudinal axis of the section and sincethey face in the same direction as the overall opening angle of thewalls of the section, it is possible to strike out these ribs byemploying a non-collapsible die. If the faces of each rib make an angleto each other much less than a right angle as shown for example in Fig.10, then it becomes necessary to form the ribs by employing a relativelyexpensive and complicated collapsible die with its attendant likelihoodof non-uniformity of. the finished ribs. Furthermore, since in thepreferred form of rib shown in Fig. 9, thefaces 28 are substantiallyperpendicular to the flange i2, and since the tendency is for thesection to collapse along a line drawn between and parallel to thecorners 22, the ribs prevent this initial buckling, and subsequentcollapse and folding of the section along the said corner portions.While it is preferred'to form the ribs in parallel linear shape, it willbe obvious that these ribs may be arcuate or any other shape so long asthey do not extend around the entire periphery of the metal section. Itshould be noted of course that the ribs are confined to the flat sideportions of the section 5 and do not appear in the rounded end portionsof the section.

During the foregoing described rib forming operation the lower circularrim 23 is formed with a slightly smaller taper than the portion 24. Inthe next two trimming operations, the bottom 25 is cut out and thetapered flange 23 is trimmed straight to remove any excess material. Thefinished truncated funnel-shaped section is. then of the shape shown incross section in Fig. 8.

The sealing ring I as above pointed out is made in two parts 8 and 9,shown respectively in Figs. 11 and 12. The part 8 is sealed to thepreformed glass flare 2 of the glass neck, preferably although notnecessarily, as described in said Patent No. 2,194,418, and in orderthat a vacuum-tight seal may be effected the flare 2 may be of Coming705 AJ glass, and the part 8 may be of Kovar." The part 3 which may beof steel is preferably provided with an annular grooved rim 28 which isadapted to receive the rimflofpartl. Theparts3and8arecopper brazed andthe copper which lies in the groove 8 23 serves as a vacuum-tight sealbetween the parts. Part 3 is provided with an enlarged rim 28 having aslight taper corresponding to and mating with the taper 23 so that theseparts overlap each other snugly as shown in Fig. 14.

Before the rim 28 of the sealing ring is seam welded to the rim 23, itmust be preliminarily "basted thereto in a perfectly coaxial manner.This basting may be in the form of four equidistant spot welds aroundthe overlapped rims 21, 23. If this preliminary fastening of the partsby spot welding is omitted the subsequent seam welding may result in thefastening of the sealing ring to the section 5 in a non-coaxial manner,because of the heat and strains attending the seam welding operationwhich tend to distort the overlapped rims 21, 23. This is particularlyimportant when the flare 2 is preformed by a precision process asdescribed in said Patent No. 2,194,418. I have found that thispreliminary 25 basting enables the tube as a whole to be built with thegreatest precision, thus adapting it to economical quantity production.

In order to spot weld the sealing ring and section 5 in a perfectlycoaxial manner, a special jig 80 such as shown in Fig. 15 is employed.This jig comprises a flat metal base 29 preferably having a smoothmachined upper surface against which the flat flange I2 of section Irests and against which it may be rigidly clamped by a set of 85clamping strips 38 and bolts 3|. The base 29 is formed with a pair ofvertical standards 32, 33, having right-angled top portions 34, 35,which support the internally threaded ring 36 which is thus accuratelyand rigidly fastened so that it is 4 coaxial with the center of base 29.Removably threaded within ring 36 is an externally threaded ring 31which is'adapted to engage the shouldered portion 38 of the sealingring.In using the jig. the clamping members 38 are loosened I and the section5 is placed on base 29 as shown, and if desired the base may be providedwith gauging lugs to automatically center the section 8 with relation tothe center of ring 36, whereupon the members 39 may be tightened toclamp the section 5 against the base. The sealing ring consisting ofpreviously united parts 8 and 9 is then assembled over the rim 23whereupon the ring 31 is threaded into ring 36 and tightened against theshoulder 38. This tightening automatically centers the sealing ring withrespect to section 5. The overlapping tapered rims 23 and 28 may then bespot welded at four equidistant points around the periphery. With theparts 2, 5, 8 and 9 thus fastened together perfectly coaxially, the rims23 and 28 may then be seam welded around their entire periphery toprovide the nec essary vacuum-tight seal therebetween.

The next step is the assembly and welding in place of the metal framedwindow shown in Fig. IB. Inorder to prevent the setting up of localizedstrains as pointed out above the flange II on the window frame and theflange l2 on section 5 must be perfectly flat so as to present a smoothsurface for welding. The uniformity of the strains in the glass windowresulting from the outside air pressure during and after exhaustion ofthe tube, depends also on the flatness of shoulder 19 which receives thethrust of the window which is seated thereon.

When it is remem- .73.

bered that the window may be of the order of inches by 12 inchesdiagonally, in order to prevent the envelope collapsing, it is necessaryto employ relatively heavy gauge sheet metal. However by making thesection I with its shoulder ll and flange i i as described above, it ispossible to employ relatively lighter gauge metal without danger ofdistortion of the necessary flat surfaces. As an additional precautionthe window should also be provided with a specially flattened rim H anda resilient gasket should be inserted between this rim and shoulder i9.I have found that a gasket that is well suited for this purpose consistsof a strip or tape formed of woven glass threads such as are employed inso-called woven glass cloth, a section of this gasket being shown inFig. 18.

The window as shown in Fig. IO comprises a metal frame having the outerflat rim or flange Ii and a flat inner rim 39 which is sealed into therelatively thick glass It) in a vacuum-tight manner. For a detaileddescription of one preferred manner of sealing the frame to the glass,reference may be had to Patent No. 2,178,826. As pointed out in saidapplication, the thrust of the window is against the shoulder i9, andpreferably in accordance with the present invention the glass isprovided with a marginal ridge or rim M which has its bearing facesmoothly flattened. Fig. 17 shows a section of the window and thestraightening and flattening press for the rim N. This press consistsessentially of two flat plates 40, 4| between which the window isplaced. Plate 40 is conveniently placed in an oven whereupon the windowwith its previously sealed-in frame is placed upon plate 40 and coveredby plate 4|, 2. suitable weight, for example 12 to 40 pounds beingplaced on plate 4 i The oven is then heated to the annealing temperatureof the glass and annealed through the standard annealing schedule forthe particular glass used. At the annealing temperature the glass issoft enough so that the rim it takes the flat shape of plate l0. fhecooling during the annealing schedule ensures the elimination ofresidual stresses in the glass. Consequently since the rim I4 isperfectly flat, when the window is welded to flange I! with theresilient gasket i3 in place, the strains due to atmospheric pressureare uniform around the entire periphery of the window. Inasmuch as it israther difl'icult to employ a single length of the woven glass tape i3without bunching it at the corners, it is preferred to employ fourseparate lengths which are then inserted only along the straightportions of the window frame. It will be understood that instead ofusing a gasket in the form of woven glass flbres, well known glass woolmay be used for this purpose.

While specific materials and dimensions have been mentioned herein, itwill be understood that the invention is not necessarily limited theretoand that various changes and modifications may be made without departingfrom the spirit and scope of the invention. For example, while certainof the metal parts are sealed together preferably by aseam weldingprocess, it will be understood that they may be sealed by copper brazingor the like.

What I claim is:

1. A cathode ray tube envelope including a funnel-shaped metal bodyportion having a flat radial flange and a window receiving shoulder atits large end, a glass window having a metal flanged frame sealed aroundthe edge of the window, the flange of said frame being flat and sealedin a vacuum-tight manner to the flrst mentioned flange, said windowhaving a flat marginal ridge where it rests on said shoulder wherebylocalized strains on said window are avoided.

2. A cathode ray tube envelope according to claim 1 in which saidshoulder is provided with a flat wall to engage said flat ridge on thewindow.

3. A cathode ray tube according to claim 1 in which a resilient gasketis positioned between the rim of the window and said shoulder toequalize the mechanical stresses in the window.

4. A window for a cathode ray tube or the like comprising a glass body,a metal frame sealed directly into and around the margin of said glassbody said frame having a substantially flat supporting flange and.amarginal supporting ridge on said window said ridge having a flat smoothface whereby localized strains on the window are avoided.

5. A cathode ray tube envelope including a funnel-shaped metal bodysection substantially rectangular in shape with rounded corners andhaving a plurality of spaced ribs on at least one side wall thereof saidribs terminating short of said corners and extending transversely to thelength of the tube.

6. A cathode ray tube according to claim 5 in which the corners of thefunnel-shaped section are rounded and the said ribs merge into saidcorners but without extending beyond the said corners.

7. A cathode ray tube envelope according to claim 5 in which the raisedfaces of the ribs make only a slight angle with relation to thelongitudinal axis of the section.

8. A cathode ray tube according to claim 5 in which said ribs aresubstantially right-angled in cross section.

9. A cathode-ray tube envelope including a funnel-shaped metal bodysection having a glass window sealed to the larger end thereof, arebottom of said recess to equalize the strains around the margin of theglass window, said window being sealed tosaid larger end in avacuum-tight member independently of said gasket.

10. A cathode-ray tube according to claim 9 in which the said gasket isof a porous vitreous material.

11. An evacuated cathode-ray tube including a funnel-shaped metal bodysection, the larger end of said section being provided with a shoulderedseat, a massive glass window having its margin seated against saidshoulder to support the window against atmospheric pressure and a porousresilient gasket interposed between said window and shoulder to equalizethe strains in

